The invention relates to a method for the accurate positioning of a measurement object to be examined aerodynamically, especially a vehicle. Furthermore, it relates to an apparatus for implementing this method.
FR 2 641 378 A1 shows the measurement section of a wind tunnel for the aerodynamic investigation of aircraft on a model scale. To be specific, aerodynamic investigations are to be carried out not only in the horizontal position of the aircraft model in relation to the air flow, but the flow relationships are also to be tested in rising or falling flight. For this purpose, there is arranged in the measurement section of the wind tunnel a device for holding the aircraft model, with which it can be held in a stationary position in the measurement section at different angles of attack. Provided in the device is a carrier which is bent in a semicircle and extends vertically through the measurement section in the area downstream of the measurement object, its centre of curvature being arranged in approximately the same position as the spatial centre of the measurement section. The carrier is configured so as to have beneficial flow properties in the air flow direction. At the centre of the carrier, an arm projects down in the, direction of the circle centre of the carrier and, at its free end, crries the aircraft model with carrying surfaces that are arranged at the same height on both sides, the arm being rigidly, connected to the tail of the vehicle model and being aligned with the aircraft fuselage. The upper and the lower end of the semicircular carrier is in each case connected by a join to horizontal guides that are aligned in the air flow direction and are arranged above and below the measurement section. In specific terms, the upper end of the carrier is pivotably articulated directly to a guide carriage; whereas the lower end of the carrier is coupled to two carriages guided in parallel, with the interposition of a Y-shaped rocker. In order to set different angles of attack, the upper carriage and the lower carriages of the semicircular carrier can be displaced simultaneously in the opposite direction over presettable displacement travels, so that although the carrier and the aircraft model fastened to it change their angular position in space, the position of the model in the measurement section remains virtually unchanged in the air flow direction. The movable mounting of the aircraft model in the known wind tunnel has, in terms of function, a certain correspondence with a turntable, such as is usually provided in the floor of the measurement section of vehicle wind tunnels. By means of such a turntable, the intention is for the vehicle positioned in the measurement section to be capable of being pivoted with its longitudinal axis into different angular positions in relation to the flow directions, in order in this way to be able to investigate lateral wind influences.
A wind tunnel is an installation which is not only complicated technically but also very expensive in, operation. On the other hand, however, wind-tunnel measurements are imperative, especially in the motor vehicle industry. The measurement object must be aligned in this case quite accurately in the wind tunnel and must assume an exactly predefined position. Until the latter is ensured, a relatively long time elapses, in which, basically, costs occur without any measurements being carried out.
Neither the turntable which is known from vehicle wind tunnels and provided in the floor of the measurement section, nor the device disclosed by FR 2 641 378 A1 for holding an aircraft model in different spatial positions, provides any points of approach to solving the problem of spatially exact pre-positioning of the vehicle on the turntable or of an aircraft model on the carrying arm. In any case, neither the turntable nor the disclosed holder of the aircraft model can be used for such exact positioning operations of the measurement object in the measurement section. Only after the measurement object has been pre-positioned in an exact relative position on the turntable of a vehicle wind tunnel, or has been fixed to the carrying arm of the aircraft wind tunnel, can the desired test position of the measurement object in the measurement section be moved to by means of the turntable and/or the manipulation equipment. It is only subsequently possible for the desired test position of the measurement object to be adjusted with the accuracy with which the measurement object was previously aligned and fastened on the turntable and/or on the manipulation equipment. However, for successful development activity, it is very important that the test conditions are known reliably and are predefined with high accuracy.
Consequently, there is the object of the present invention to provide a method of accurately positioning a measurement object to be examined aerodynamically in such a way that it permits a reduction in the wind-tunnel costs. Furthermore, the object of the invention is to provide an apparatus for implementing this method.
The method features of this claim is that accurate alignment of the measurement object is performed outside the wind tunnel and this measurement object is subsequently taken into the interior of the wind tunnel, in particular at the location predefined for the measurement, in such a way that the measurement position is assumed without further correction and is also maintained for the entire duration of the measurement. The costs for this measurement can therefore be reduced quite decisively, since the wind tunnel is truly only used when the envisaged measurements are also being carried out in it.
The critical factor in this method is therefore not only the correct alignment of the measurement object at any desired location outside the wind tunnel, but also its transfer whilst maintaining the adjustment previously carried out. The core of this invention is the use of a measurement-object carrier, on which the measurement object can not only be held such that it cannot be moved but can also be aligned exactly. Furthermore, this measurement-object carrier must be designed in such a way that, following its transport into the wind tunnel, the measurement object assumes the exact position which is correct for the measurement in the said tunnel, and the measurement is not influenced or even disrupted by the said measurement-object carrier. Furthermore, it must be capable of taking the measurement object out of the wind tunnel again following the measurement.
The result of this is that, in relation to the wind-tunnel costs, it is unimportant how long the alignment of the measurement object with respect to the measurement-object carrier lasts, since the associated operations can be carried out while, for example, another measurement object is being subjected to measurements in the wind tunnel. The alignment of the measurement object on the measurement-object carrier can be carried out in a similar way to the previous alignment in the wind tunnel, that is to say in this case a characteristic reference line on the measurement object is used, this line having a specific relative position in relation to the axis of the wind tunnel in the measurement section during measurement. In the method according to the invention, this reference line is registered in the X, Y and Z direction outside the wind tunnel. During the transfer from the preparation position outside the wind tunnel into the measurement position in the wind tunnel, the set position of the vehicle is maintained in all three axial directions.
Cones and mating cones are a means which are technically most suitable to bring two objects into a three-dimensionally correct mutual position. The present invention also provides the preconditions for a trouble-free transfer of the measurement-object carrier to the wind tunnel and its measurement section on the floor. To drive in the transport direction to a correct stopping point in the wind tunnel is a technical problem neither during transport by hand nor during automatic transport. After stopping at the accurate point, the only action which follows is lowering in order that the cones can enter the locally fixed mating cones, and then at the same time the correct alignment of the measurement object, especially the motor vehicle, in the-wind tunnel is therefore achieved.
As already mentioned, the measurement-object carrier must not impair or falsify the measurements and really should not interfere. To this extent, a configuration according to the present invention is particularly advantageous.
The measurement-object carrier is set down on a turntable (known per se) in the area of the measurement position of the wind tunnel. This turntable, with its reference line, which is located in the wind-tunnel axis during measurement, is rotated into the direction of travel of the measurement-object carrier as the measurement-object carrier is moved into the measurement position or removed from the same. And after the measurement object has been set down on the turntable, both are pivoted, together with the reference line or the longitudinal mid-axis, into the longitudinal axis of the wind tunnel. The measurement-object carrier then only needs to be moved radially towards the centre of rotation of the turntable or away from it. This has the advantage that curved paths when the measurement-object carrier is being moved in or out can be avoided.
If the measurement object is a motor vehicle, which stands on the tires both normally and during the measurements, then it is possible not to set it down on. the standing surfaces of the tires on the measurement-object carrier, if it is to be transferred quickly, reliably and accurately to the measurement section in the wind tunnel.